Portable communication device with optimized transmission loss

Abstract

A portable electronic apparatus is disclosed having an antenna and a communication circuit. The antenna impedance is chosen to be a predetermined value which is deliberately mismatched to the impedance of the communication for a predetermined frequency band. This mismatch is chosen to optimize the signal loss between the antenna and the communication circuit when the antenna is far and near a disturbing source. The imaginary part of the antenna impedance has a sign opposite to the sign of the circuit impedance when the antenna is a predetermined distance from the disturbing source.

I claim: 
     
       1. A portable communication device having a device impedance and comprising an antenna having an antenna impedance, wherein the antenna impedance has a predetermined value which is mismatched to the device impedance within a frequency band of interest, for equalizing a transmission loss between the antenna and the communication device as a function of a distance between a disturbing object and the antenna, wherein an imaginary part of said antenna impedance has a sign opposite to a sign of said device impedance when the antenna is a predetermined distance from said disturbing object. 
     
     
       2. The portable communication device as claimed in claim 1 wherein, when the distance between the antenna and the disturbing object is decreased, the mismatch is arranged so as to lower the transmission loss between the antenna and the communication device in comparison with the transmission loss when the communication device and the antenna are matched. 
     
     
       3. A portable communication device having a device impedance and comprising an antenna having an antenna impedance, wherein the antenna impedance has a predetermined value which is mismatched to the device impedance within a frequency band of interest, for equalizing a transmission loss between the antenna and the communication device as a function of a distance between a disturbing object and the antenna, wherein a ratio between the antenna impedance and the device impedance fulfils the following conditions: a first one of these the device and antenna impedances has a substantially real value for free space conditions, and   a second one of these the device and antenna impedances has a real part having a value in the range of 35%-70% of the value of the first impedance and an imaginary part in the range of 5%-30% of the value of the first impedance, within the frequency band of interest, the imaginary part having a sign opposite to the sign of the imaginary part of the first impedance when the antenna is 0.2λ from said disturbing object.   
     
     
       4. A portable electronic apparatus having an antenna and a communication circuit, wherein a predetermined antenna impedance of said antenna and a circuit impedance of said communication circuit are mismatched for a predetermined frequency band to optimize a signal loss between said antenna and said communication circuit when said antenna is far and near a disturbing source, an imaginary part of said antenna impedance having a sign opposite to a sign of said circuit impedance when the antenna is a predetermined distance from said disturbing source. 
     
     
       5. The portable electronic apparatus of claim 4 wherein the predetermined distance is 0.2λ, where λ is a wavelength of operation of said apparatus. 
     
     
       6. The portable electronic apparatus of claim 4 wherein the one of said antenna impedance and said circuit impedance has a substantially real value for free space conditions, and another of said antenna impedance and said circuit impedance has a real part having a value which is approximately 35%-70% of said one impedance and an imaginary part which is approximately 5%-30% of said one impedance.